lesson
Outer electrons help explain group behaviour
1 · Learn
In a simplified shell model for early elements, electrons occupy shells and the outer-shell arrangement helps explain related chemical behaviour. A neutral sodium atom has arrangement 2,8,1 in this model.
Shell diagrams are models rather than literal circular tracks. Use them within their intended scope and distinguish losing an electron from losing a proton.
2 · Worked example
Losing sodium's outer electron gives an ion with arrangement 2,8 and charge +1.
3 · Your turn
Why is the sodium ion positive after losing one electron?
Check your answer
It now has one more proton than electron; a negative electron was removed.
4 · Apply your learning
Compare early-element diagrams and relate outer electrons to a predicted ion charge, stating the model's limited scope.
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Check a calculation · Year 5 onward
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Powers, roots and trigonometry · Year 7 onward
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